The present invention relates generally to elastic fabrics used in the construction of garments, and, more particularly, to elastic fabrics having conductive wiring affixed to the fabric for use in garments intended for physiological monitoring of prescribed body functions.
As the administration of health care services has shifted from hospital-based or office-based care to home-based or patient-borne self care, strides have been made in the development of devices and garments for monitoring physiological signs, while allowing patients to maintain lifestyles as normal as practical. Thus, traditional invasive-type devices could not be used for such purposes. To overcome the inherent risks in these invasive monitoring devices, non-invasive devices have been developed for adaptation in conventional garments or have been worn on some part of the body; e.g., wristwatch-like.
The development of these new non-invasive devices has paralleled advances in systems for monitoring vital signs and for communicating this information, particularly when abnormal, directly to the patient as well as to health care providers through a variety of means, including infrared links. However, these devices heretofore have not provided the level of reliability and accuracy necessary for monitoring certain health conditions or vital signs.
There is known in the art a non-invasive physiological monitoring system comprising a garment in the form of a shirt, multiple inductive plethysmographic sensors attached to and supported by the garment, a transmitter attached to the garment and to the multiple sensors for transmitting signals from the garment, and a processor unit remote from the garment for receiving the signals and sending messages back to the patient. The sensors comprise ends of conductive wire attached to the garment at the measurement points for the physiological signs. The sensors have been attached to the garment in a prescribed curved configuration, desirably sinusoidal, so that as the body expands and contracts the sinusoidal pattern changes with a corresponding change in inductance in the wires. Inductance is the input into the transmitter that is subsequently translated into a physiological reading. However, the manner in which these conductive wires have heretofore been attached to the shirt have led to less than optimal accuracy and reliability as the relative locations of the wires in the garments have shifted or the attachment points have degraded. For example, conductive wires have been adhered to paper substrates and subsequently attached on or within sleeves of the garment adapted for their placement. While these constructions have advanced the art of physiological monitoring, they have not proven satisfactory for consistent, long-term performance; e.g., paper substrates wear and tear and conductive wires lose their designed configuration for proper monitoring.
The present invention relates to a fabric for use in apparel of the type used for physiological monitoring of prescribed human body functions. In the preferred embodiment, this fabric includes an elongated band of elastic material that is stretchable in the longitudinal direction, and at least one conductive wire incorporated into or onto the elastic fabric band in a prescribed curved configuration. As the fabric stretches, the curvature of the conductive wire changes. As this occurs, the inductance of the conductive wire varies, and is measured and processed by an attached or monitoring unit. An object of the present invention is to provide a fabric and conductive wire construction that will provide reliable, consistent, and long-term performance.
The elongated band of elastic material may be formed in any of the conventional ways for forming elastic fabric. These include warp knitting, weft knitting, weaving, braiding, or forming in a non-woven construction. Warp knitting is preferable because conventional crochet machines are adaptable to form bands of elastic having narrow widths. The elastic band of the present invention is desirably xc2xe to I V2 inches wide, but may be as narrow as xc2xc inch. The elastomeric material used to form the elongated band of elastic material is desirably Lycra(copyright) or Spandex(copyright) because of their superior elasticity. Additionally, because these man-made filaments are not abrasive or irritating to the skin, they arc quite suitable for applications where the elastomeric material is in direct contact with the skin. However, for most applications, natural extruded filaments of latex may be used for the elastomeric material.
In forming the elastic band on a conventional crochet machine, such as a machine manufactured by Jacob Mxc3xcller as Model RD3-8/420 (Jakob Mxc3xcller of America, Inc., Charlotte, N.C.), the elastic filaments form the warp beams in a longitudinal direction. The fill, or weft, may be formed from a variety of yarns including, not limited to, single-ply, 150 denier polyester; 2-ply, 70 denier nylon; 2-ply, 100 denier polyester; and, 2-ply, 150 denier polyester.
At least one conductive wire is incorporated with the elastic fabric. As used herein, xe2x80x9cincorporatedxe2x80x9d means that the conductive wiring is either intermeshed with the elastic fabric structure or operably affixed to at least one face of the elastic fabric. Copper wire in the 27 American wire gauge (xe2x80x9cAWGxe2x80x9d) to 28 AWG range has been found most suitable for knitting on crochet machines; however, as those skilled in the art will appreciate, other sizes may be used depending upon the particular machine and machine setup being employed. One such suitable wire is NE 12544 TR Tinned Copper Wire, available from New England Electric Wire Corporation of Lisbon, New Hampshire. The wire may be either braided or stranded and coated or uncoated as long as it may be shaped and incorporated into the fabric in a prescribed curved configuration, preferably sinusoidal.
For monitoring certain physiological functions where a higher degree of sensitivity and accuracy is required, multiple wires are interconnected in a garment to form a single continuous conductive circuit that encircles the monitored area a number of times corresponding to the number of wires. Where multiple conductive wires are required, they may be affixed to a single elastic fabric band so that they are substantially in parallel relation or are in substantially overlapped relation. Once the elastic fabric band is incorporated into a garment, the wires may be interconnected.
While knitting the conductive wire into the fabric structure at the time of forming the elastic band is most efficient and economical, the conductive wire may be sewn to at least one surface of an elastic fabric band in a separate manufacturing step subsequent to formation of the elastic fabric band. Accordingly, this subsequent attachment may be performed either manually or automatically.
Alternatively, the conductive wire and fabric structure may be formed in a braided construction. Formed in this manner, a number of groupings of elastomeric fibers or filaments may be intertwined by braiding. One of the groupings of fibers or filaments will carry a conductive wire, coated or uncoated. The size and number of elastomeric fibers or filaments in each grouping, in combination with the number of groupings, will determine the size of the sinusoidal pattern of the wire. This braiding technique results in a more compact construction that will stretch and contract, providing an output signal to a monitoring unit.
As a further alternative, the conductive wire and fabric structure may be formed in axcx9cnon-woven construction. At least one conductive wire, shaped in a sinusoidal arrangement, is placed in a long narrow mold. Manufactured filaments; e.g., polyester, nylon, etc., are extruded and crisscrossed over at least one side of the shaped wire to form a web or mesh-like overlay. Finally, a film of elastomeric material is extruded to encapsulate one or both surfaces of the wire and web layers. When cooled and dried, this structure will stretch and contract to deliver a satisfactory, reliable output signal.
These and other aspects of the present invention will become apparent to those skilled in the art after a reading of the following description of the preferred embodiment when considered with the drawings.